Property Test of the Q-Factor for High Purity Copper at the Temperature of 20K
0
Citation
0
Reference
20
Related Paper
A cryogenic C-band photocathode RF-gun operating at 20 K is under development at LEBRA in Nihon University. The RF-gun is of the BNL-type 2.6-cell pillbox cavity with the resonant frequency of 5712 MHz. The 6N8 high purity OFHC copper (corresponding to RRR-3000) is used as the cavity material. From the theoretical evaluation of the anomalous skin effect, the quality factor Q of the cavity at the operating temperature of 20 K has been expected to be approximately 60000. The cavity basic design and the beam bunching simulation were carried out using Poisson Superfish and General Particle Tracer (GPT). Machining and diffusion bonding of the RF-gun cavity was carried out in KEK. After diffusion bonding the Q0 value of the -mode resonance at the room temperature (23.5 °C) was approximately 11440.
Photocathode
Electron gun
Klystron
Cavity wall
Cite
Citations (0)
Jefferson Lab (JLab) processed six nine-cell cavities as part of a small-scale production for LCLS-II cavity processing development utilizing the promising nitrogen-doping process. [1] Various nitrogen-doping recipes have been scrutinized to optimize process parameters with the aim to guarantee an unloaded quality factor (Q 0) of 2.7·1010 at an accelerating field (Eacc) of 16 MV/m at 2.0 K in the cryomodule. During the R&D phase the characteristic Q0 vs. Eacc performance curve of the cavities has been measured in JLab’s vertical test area at 2 K. The findings showed the characteristic rise of the Q0 with Eacc as expected from nitrogen-doping. Initially, five cavities achieved an average Q0 of 3.3·1010 at the limiting Eacc averaging to 16.8 MV/m, while one cavity experienced an early quench accompanied by an unusual Q 0 vs. Eacc curve. The project accounts for a cavity performance loss from the vertical dewar test (with or without the helium vessel) to the horizontal performance in a cryomodule, such that these results leave no save margin to the cryomodule specification. Consequently, a refinement of the nitrogen-doping has been initiated to guarantee an average quench field above 20 MV/m without impeding the Q 0. This paper covers the refinementmore » work performed for each cavity, which depends on the initial results, as well as a quench analysis carried out before and after the rework during the vertical RF tests as far as applicable.« less
Cite
Citations (4)
The proposed femto-second light source consists of a re-circulating linac that delivers an electron beam to an arc of superconducting undulator magnets that deliver very short pulses of X-rays to materials science experiments. Superconducting RF cavities accelerate the electrons through the re-circulating linac. The design acceleration gradient for the 1300 MHz RF cavity system is 25 MV per meter. TESLA cavities operating in CW mode can provide this level of acceleration. This report presents the parameters of the proposed femto-second light source superconducting linac. Each nine-cell cavity will generate 44 W of AC loss at 1.9 K. The AC loss is added to the other losses in the accelerator cavity system. The superconducting RF cavity losses and linac refrigeration requirements are summarized in this report.
Undulator
Superconducting radio frequency
Cite
Citations (0)
Quarter (Canadian coin)
Cite
Citations (0)
Cite
Citations (0)
A superconducting wiggler with a magnetic period of 6.0 cm (SW6) and a peak field of 3.2 T has been designed and fabricated in the National Synchrotron Radiation Research Center (NSRRC). The beam duct separates the electron beam from the cryogenic system of the magnet. The heat load on the beam duct should be low to stabilize the operation of the superconducting magnets. However, outgassing caused by synchrotron radiation at an electron energy of 1.5 GeV and a current of 200 mA must be reduced. Accordingly, operating the system at a higher temperature can minimize the adsorption of molecules on the beam duct. Therefore, the beam duct system and its connection by finite element analysis are designed to optimize the operating temperature of the beam duct at between 100 and 120 K. Performance of the beam duct is established to comply with specifications during the operation of magnet
Wiggler
Cite
Citations (5)
A two-cell 425-MHz drift-tube linac (DTL) ''sparker'' for operation at 20 K has been designed and constructed to operate at >2 Kilpatrick accelerating voltage while transporting an H/sup /minus// 5-MeV beam at currents up to 100 mA. Permanent-magnet quadrupole (PMQ) assemblies are installed in the input/output beam-transport system and in the cryogenically cooled cavity drift-tube and two half-cells. The cavity, cooled by a 700-W cold-helium gas refrigerator, is mounted inside a superinsulated high-vacuum chamber that is evacuated by a 360-/ell//s turbomolecular vacuum-pump system. The cavity components (slug tuner, post coupler, drive loop) are fabricated from electropolished OFHC possessing a residual resistivity ratio of >200. The rf contacts for the cavity end walls are copper-plated Inconel X-750 C-seals. The drift-tube stem, post-coupler stem, and slug tuner use gold-plated beryllium/copper Multilam bands rf contacts. Initial experiments at 20 K have shown a cavity Q enhancement of 4-5. The experimental program includes characterization of the rf cavity beam loading, engineering design and construction, and thermal system response. 11 refs., 2 figs.
Tuner
Cryostat
Drift tube
Quadrupole magnet
Cavity wall
Cite
Citations (0)
A superconducting rf linac has been required to realize high-duty operation and low-electricity consumption for a high-average-power and high-efficiency free-electron laser (FEL). The JAERI FEL superconducting linac consists of a 250 kV electron gun, a subharmonic normal-conducting buncher (SHB) of 83.3 MHz, and two single-cell and two five-cell superconducting cavities of 499.8 MHz. The gun was typically operated around 200 kV to reduce space-charge effects. A combination of the SHB and the two single-cell cavities enabled a high-current beam of more than 10 A by utilizing a thermionic cathode and a grid pulser. The full width at half maximum bunch length and energy resolution were measured to be 22 ps and 1% or less, respectively. The measured results agreed with calculations utilizing the modified PARMELA code. This showed the validity of the linac design for the FEL. With this beam quality, high-average FEL power of 0.1 kW at a 24–28 μm wavelength was obtained in a quasi-cw mode.
Free-electron laser
Electron gun
Duty cycle
Cite
Citations (3)
The design goal for the TESLA Test Facility Linac is an accelerating gradient of 15 MV/m at a quality factor of Q=3/spl middot/10/sup 9/. In the linac the cavities are operated in pulsed mode (constant gradient for 800 /spl mu/s with 10 Hz repetition rate). The majority of the first 17 industrially produced cavities exceeded the specification. Several cavities reached 25 MV/m at Q>1/spl middot/10/sup 10/. Due to cleaning by high pressure water rinsing most of the cavities showed no field emission loading; the major limitation was thermal instability. In cavities with poorer performance, two types of field limitations were identified by temperature mapping and further surface analysis: tantalum impurity in the bulk niobium and defects in the equator welds. Eight cavities, equipped with main power coupler, HOM couplers and tuning system have been successfully tested in a horizontal cryostat in pulsed mode. Also here the majority of the cavities exceeded the design goal and gradients up to 25 MV/m could be achieved.
Cryostat
Cite
Citations (7)
Superconducting Super Collider
Cryogenics
Superconducting Coils
Cite
Citations (1)